sql: Internal sessions exempt from disallow_full_table_scans setting

Previously, enabling the cluster setting
sql.defaults.disallow_full_table_scans.enabled prevented the creation of
indexes due to the internal table scans required during the process.
This change ensures that the setting is bypassed for internal
operations, while still applying to user queries.

Epic: None
Closes: #137404
Release note (bug fix): Internal scans are now exempt from the
sql.defaults.disallow_full_table_scans.enabled setting, allowing index
creation even when the cluster setting is active.

pkg/sql/internal.go

@@ -94,6 +94,7 @@ func NewInternalSessionData(
 	sd.SequenceState = sessiondata.NewSequenceState()
 	sd.Location = time.UTC
 	sd.StmtTimeout = 0
+	sd.DisallowFullTableScans = false
 	return sd
 }
 

pkg/sql/logictest/testdata/logic_test/create_index

@@ -440,6 +440,27 @@ CREATE INVERTED INDEX ON opclasses(c DESC)
 statement ok
 CREATE INVERTED INDEX ON opclasses(a DESC, c)
 
+# Regression test for GH issue #137404
+subtest disallow_full_table_scans
+
+let $disallow_full_table_scans
+select value from [show cluster settings] where variable = 'sql.defaults.disallow_full_table_scans.enabled';
+
+statement ok
+SET CLUSTER SETTING sql.defaults.disallow_full_table_scans.enabled = true;
+
+statement ok
+CREATE TABLE t_disable_full_ts (id UUID PRIMARY KEY);
+
+statement ok
+CREATE INDEX ON t_disable_full_ts (id);
+
+statement ok
+SET CLUSTER SETTING sql.defaults.disallow_full_table_scans.enabled = $disallow_full_table_scans;
+
+statement ok
+DROP TABLE t_disable_full_ts
+
 subtest create_index_on_materialized_view
 
 statement ok
@@ -521,3 +542,25 @@ CREATE INDEX IF NOT EXISTS idx ON tbl_ifne (b) STORING (a)
 
 statement ok
 DROP TABLE tbl_ifne CASCADE
+
+subtest disallow_full_table_scans
+
+let $disallow_full_table_scans
+select value from [show cluster settings] where variable = 'sql.defaults.disallow_full_table_scans.enabled';
+
+statement ok
+SET CLUSTER SETTING sql.defaults.disallow_full_table_scans.enabled = true;
+
+statement ok
+CREATE TABLE t_disable_full_ts (id UUID PRIMARY KEY);
+
+statement ok
+CREATE INDEX ON t_disable_full_ts (id);
+
+statement ok
+SET CLUSTER SETTING sql.defaults.disallow_full_table_scans.enabled = $disallow_full_table_scans;
+
+statement ok
+DROP TABLE t_disable_full_ts
+
+subtest end